Effect of Ni and TiO₂on hydrogen generation from aqueous solution with non-thermal plasma

Abstract

Research was performed to increase the efficiency of a plasma reactor for the H2 yield. Ni as a transitional metal catalyst and TiO2 as a photocatalyst were utilized for the generation of H2 from an aqueous solution. The composition of aqueous solution, discharge properties and electrode geometry affected H2 generation. It was found that the hollow type electrode configuration allowed discharge distribution along the perimeter of the electrode's tip, which increased the density of streamers and reduced plasma energy loadings, as the value of the inception voltage for the discharge propagation decreased. The maximum H2 yield was observed at 2 kHz of discharge frequency and 12 kV of applied voltage, using distilled water, which was in compliance with a steep increase in electron density, ne ≈ 1017 cm−3 and electron temperature, Te ≈ 2 eV. Within this favourable discharge condition, the synergistic effect of a non-thermal plasma and TiO2, Ni catalysts was investigated. The plasma state was studied by optical emission spectroscopy (OES), electrical and acoustical techniques. Emitted light, electric current and acoustical signals acquired from the discharge demonstrated systematical correlation. OES was used to estimate ne and Te by measuring the Stark broadening of the Balmer Hβ line and emission of Hα and Hβ lines ratio, respectively. The rotational and vibrational temperatures were deduced from OH(A 2Σ+–X 2Π, Δυ = 0) and N2(C 3Πu–B 3Πg) bands.

Pyrite-enhanced methylene blue degradation in non-thermal plasma water treatment reactor

“…The most probable source of OH radicals produced in the NTP reactor is the high energy electron impact dissociation of water molecules [16] as well as the photo chemical water dissociation resulting from application of the plasma [17,18] according to the following reactions:…”

Non-thermal plasmas in and in contact with liquids

“…The authors refer to their discharge as a corona discharge and use oxygen as the input gas. A similar geometry is investigated by Kostyuk et al [160] although they used pulsed excitation.…”

Effect of temperature on methylene blue decolorization in aqueous medium in electrical discharge plasma reactor

“…13,14 In addition, hydrogen (H 2 ) generation from water in hybrid gas-liquid systems has also been reported as a clean energy source of fuel [15][16][17] as well as the inactivation of micro-organisms by discharge plasma for water treatment, 18 are among other NTP applications.…”

“…15 In addition, UV light generated by the discharge plasma also enhances the water and H 2 O 2 dissociation reaction in the gas phase and at the gas-liquid interface and increase the formation of OH radicals. 15,16 Besides no control experiments were perform in this work in order to estimate the effects of UV radiation, it is well established that discharges in and in contact with liquids generate intense UV radiation. 15,16 The effect of UV radiation contribute to the decomposition of water vapor at gas phase leading to OH radicals production and promoting hydrogen generation in plasma chemical reactions.…”

“…15,16 Besides no control experiments were perform in this work in order to estimate the effects of UV radiation, it is well established that discharges in and in contact with liquids generate intense UV radiation. 15,16 The effect of UV radiation contribute to the decomposition of water vapor at gas phase leading to OH radicals production and promoting hydrogen generation in plasma chemical reactions. It was also observed that UV light generated in the gas phase above the water surface can penetrate into the water, leading to OH radicals production directly at the gas/liquid interface.…”